Display device and method of designing display device

ABSTRACT

A display device having a liquid crystal display element ( 30 ) transmitting light projected from a light source to an watching point side, and including pixels ( 31 ) forming a first image region and a second image region, and an image separation filter ( 32 ) disposed from the pixels ( 31 ) through glasses ( 33, 34 ) each with a specified thickness and forming a first image separation mechanism and a second image separation mechanism, in which a calculation for obtaining the disposing interval (P 1 , P 3 ) of each of the above-described image separation mechanisms of the image separation filter ( 32 ) is carried out on the basis of angles of elevation θk+1, θk, angles αk+1, αk, thicknesses W 1 , W 2  and refractive index n of the glasses ( 33, 34 ), a distance D from the watching point to the display device, and an interval (P 2 ) between the image regions of the above-described pixels ( 31 ) to dispose the image separation mechanisms of the above-described filter ( 32 ) with the obtained P 1 , P 3.

RELATED APPLICATION DATA

This application is a continuation of application Ser. No. 10/169,645filed Jul. 3, 2002 now U.S. Pat. No. 6,956,571. The present andforegoing applications claim priority to Japanese Application No.P2000-029595 filed on Feb. 7, 2000, and PCT application No.PCT/JP01/00841 filed Feb. 7, 2001. Each of these applications isincorporated herein by reference to the extent permitted by law.

BACKGROUND OF THE INVENTION

The present invention relates to a display device and a method ofdesigning a display device, to an image separation filter used for adisplay of a stereoscopic image with a binocular disparity or parallaxor for a double view display that displays multi-views from onedisplayed image, and to a display system using the filter.

There has been developed a system of displaying two or more mixedpictures on one display plane potentially having an image separationmechanism to take out each of given original images by the imageseparation mechanism. Such a system includes a method of separatelypresenting each of two images with binocular disparity between them toeach of the right and left eyes in a two-dimensional image to reproducea three-dimensional image, or a double-view display displayingmulti-views from one displayed face, or the like.

In the image separation mechanism used in the above-described system,the mixed pictures are separated by adopting an image separation filterusing linearly polarized light rays crossing at right angles, circularlypolarized light rays, wavelengths different from each other (red andblue etc.), or the like. Although the above-described image separationfilter can be formed in a pixel on the display plane, it is difficult tomake such a filter. Thus, a method is often used in which the imageseparation filter is provided on the outside of an ordinary displayelement displaying a two-dimensional image.

Namely, there is known a method of, for example, affixing a half-waveplate for each line outside a polarizing plate (U.S. Pat. Nos.5,264,964, 5,327,285, and 5,537,144) (SID91DIGEST 840).

In FIG. 20, there are shown cross sectional views of a display devicecapable of expressing a first image and a second image alternately onlines on one display plane when being watched. The FIG. 20 shows anexample of a transparent type display device having a light sourceprovided behind the display plane with arrows in the figure representinglight beams watched by a watcher. In general, a pixel member 1 of aliquid crystal display element of an LCD is arranged to be put betweentransparent materials such as glasses 2 a and 2 b with an imageseparation filter 3 to be mounted at a specified distance apart from thepixel member 1 as shown in the figures.

The above-described pixel member 1 has an arrangement in which a firstimage region (a pixel region displaying the first image) s₁ and a secondimage region (a pixel region displaying the second image) S₂ arealternately formed, and the image separation filter 3 has an arrangementin which a first image separation mechanism e₁ and a second imageseparation mechanism e₂ are alternately formed.

FIG. 20A shows an example of the width of the image separation filter 3and the width of the pixel 1 being out of matching with each other, FIG.20B shows an example of the position of the image separation filter 3being out of matching, and FIG. 20C shows an example of light from thelight source (not shown) to a watcher being out of matching with thepixel 1 and the image separation filter 3.

As is apparent from FIG. 20, a light beam, emitted from the light sourceand passing through the first image separation mechanism toward thewatcher, must pass through the first image region. However, the lightbeam, the position of the pixel, the position and the width of theseparation filter, being out of matching with one another, allow a partof the light beam to pass through the second image region as indicatedby x mark. This caused a problem of preventing the image from beingseparated, that is, generating crosstalk. This is the same about a lightbeam emitted from the light source and passing through the second imageseparation mechanism.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a display device anda method of designing a display device by which generation of crosstalkbetween images is prevented without providing any image separationmechanism in the pixel.

A display device according to the invention is a display device having atransparent type display element transmitting light projected from alight source to an watching point side, and including pixels forming afirst image region and pixels forming a second image forming region, andan image separation filter disposed in being separated from the pixelsby a specified region and forming a first image separation mechanism anda second image separation mechanism, and the display device ischaracterized in that a disposing interval of each of theabove-described image separation mechanisms is determined by carryingout a calculation for obtaining the disposing interval on the basis ofan angle which a straight line, connecting the above-described watchingpoint and an end point of each image region of the above-describedpixels, forms with a perpendicular line from the watching point to thedisplay device, a thickness and a refractive index of theabove-described specified region, a length of the above-describedperpendicular line, and an interval of the image region of theabove-described pixels.

Moreover, it is characterized that the above-described image separationfilter in the display device according to the invention is disposedbetween the above-described watching point and the above-describedpixel, a first transparent medium is disposed between theabove-described image separation filter and the pixel, and the disposinginterval P1 of each of the above-described image separation mechanismsof the above-described image separation filter is determined by carryingout calculation of an operation expression ofP1=P2−w1{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W1, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described firsttransparent medium, a refractive index of the above-described firsttransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

Furthermore, it is characterized that the above-described imageseparation filter in the display device according to the invention isdisposed between the above-described light source and theabove-described pixel, a second transparent medium is disposed betweenthe above-described image separation filter and the pixel, and thedisposing interval P3 of each of the above-described image separationmechanisms of the above-described image separation filter is determinedby carrying out calculation of an operation expression ofP3=P2+w2{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W2, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described secondtransparent medium, a refractive index of the above-described secondtransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

In addition, it is characterized that the above-described transparenttype display element in the display device according to the invention isarranged so as to transmit light projected from the light source onto anilluminated plane disposed on the above-described watching point side,the above-described image separation filter is disposed between theabove-described light source and the above-described pixel, a secondtransparent medium is disposed between the above-described imageseparation filter and the pixel, and the disposing interval P1 of eachof the above-described image separation mechanisms of theabove-described image separation filter is determined by carrying outcalculation of an operation expression ofP1=P2−w2{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W2, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described secondtransparent medium, a refractive index of the above-described secondtransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

Moreover, it is characterized that the above-described transparent typedisplay element in the display device according to the invention isarranged so as to transmit light projected from the light source onto anilluminated plane disposed on the above-described watching point side,the above-described image separation filter is disposed between theabove-described illuminated plane and the above-described pixel, a firsttransparent medium is disposed between the above-described imageseparation filter and the pixel, and the disposing interval P3 of eachof the above-described image separation mechanisms of theabove-described image separation filter is determined by carrying outcalculation of an operation expression ofP3=P2+w1{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W1, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described firsttransparent medium, a refractive index of the above-described firsttransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

In addition, it is characterized that the first and second imageseparation mechanisms of the above-described image separation filter inthe display device according to the invention cause light to bepolarized with directions of polarization different from each other.

Moreover, it is characterized that the first and second image separationmechanisms of the above-described image separation filter in the displaydevice according to the invention are wavelength filters different fromeach other.

Furthermore, it is characterized that the above-described light sourcein the display device according to the invention is arranged so that awavelength of a light source for a left eye is different from awavelength of a light source for a right eye.

A method of designing a display device according to the invention is themethod of designing a display device having a transparent type displayelement transmitting light projected from a light source to an watchingpoint, and comprising pixels forming a first image region and pixelsforming a second image forming region, and an image separation filterdisposed in being separated from the pixels by a specified region andforming a first image separation mechanism and a second image separationmechanism, which designing method is characterized in that a disposinginterval of each of the above-described image separation mechanisms isdetermined by carrying out a calculation for obtaining the disposinginterval on the basis of an angle which a straight line, connecting theabove-described watching point and an end point of each image region ofthe above-described pixels, forms with a perpendicular line from thewatching point to the display device, a thickness and a refractive indexof the above-described specified region, a length of the above-describedperpendicular line, and an interval of the image region of theabove-described pixels.

Moreover, it is characterized that the above-described image separationfilter in the method of designing the display device according to theinvention is disposed between the above-described watching point and theabove-described pixel, a first transparent medium is disposed betweenthe above-described image separation filter and the pixel, and thedisposing interval P1 of each of the above-described image separationmechanisms of the above-described image separation filter is determinedby carrying out calculation of an operation expression ofP1=P2−w1{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W1, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described firsttransparent medium, a refractive index of the above-described firsttransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

Furthermore, it is characterized that the above-described imageseparation filter in the method of designing the display deviceaccording to the invention is disposed between the above-described lightsource and the above-described pixel, a second transparent medium isdisposed between the above-described image separation filter and thepixel, and the disposing interval P3 of each of the above-describedimage separation mechanisms of the above-described image separationfilter is determined by carrying out calculation of an operationexpression ofP3=P2−w2{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W2, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described secondtransparent medium, a refractive index of the above-described secondtransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

In addition, it is characterized that the above-described transparenttype display element in the method of designing the display deviceaccording to the invention is arranged so as to transmit light projectedfrom the light source onto an illuminated plane disposed on theabove-described watching point side, the above-described imageseparation filter is disposed between the above-described light sourceand the above-described pixel, a second transparent medium is disposedbetween the above-described image separation filter and the pixel, andthe disposing interval P1 of each of the above-describedimage-separation mechanisms of the above-described image separationfilter is determined by carrying out calculation of an operationexpression ofP1=P2−w2{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W2, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described secondtransparent medium, a refractive index of the above-described secondtransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

Moreover, it is characterized that the above-described transparent typedisplay element in the method of designing the display device accordingto the invention is arranged so as to transmit light projected from thelight source onto an illuminated plane disposed on the above-describedwatching point side, the above-described image separation filter isdisposed between the above-described illuminated plane and theabove-described pixel, a first transparent medium is disposed betweenthe above-described image separation filter and the pixel, and thedisposing interval P3 of each of the above-described image separationmechanisms of the above-described image separation filter is determinedby carrying out calculation of an operation expression ofP3=P2−w1{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)},with P2, W1, n, t, and T taken as an interval between the image regionsof the above-described pixels, a thickness of the above-described firsttransparent medium, a refractive index of the above-described firsttransparent medium, a sine function of an angle of elevation to avertical end line of the K-th (K represents an integer) pixel from theabove-described watching point, and a sine function of an angle ofelevation to a vertical end line of the (K+1)-th (K represents aninteger) pixel from the above-described watching point, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents an embodiment according to the invention with anarrangement diagram showing an example of watching a display device witha converging type filter,

FIG. 2 presents an embodiment according to the invention with anexplanatory diagram of a principal part showing an example of providinga front filter,

FIG. 3 presents an embodiment according to the invention with anexplanatory diagram of a principal part showing an example of providinga rear filter,

FIG. 4 presents an embodiment according to the invention with anarrangement diagram showing a relationship between a width of a pixeland a width of an image separation filter both on the k-th line from thefront of a watcher,

FIG. 5 presents an embodiment according to the invention with a graphexplaining how to obtain constants t and T,

FIG. 6 presents an embodiment according to the invention withexplanatory diagrams of a principal part each showing positionalarrangement of the pixel, the filter, and a light beam,

FIG. 7 presents an embodiment according to the invention with anexplanatory diagram of a principal part showing a relationship betweenthe pixel and the filter,

FIG. 8 presents an embodiment according to the invention with graphseach showing change in a width of the k-th pixel from the center of adisplay plane,

FIG. 9 presents an embodiment according to the invention with graphseach showing a relationship between a position of a head of a watcherand a width of the filter,

FIG. 10 presents another embodiment according to the invention with anarrangement diagram showing an example of watching a display device witha diffusing type filter,

FIG. 11 presents another embodiment according to the invention with anexplanatory diagram of a principal part showing an example of providinga front filter,

FIG. 12 presents another embodiment according to the invention with anexplanatory diagram of a principal part showing an example of providinga rear filter,

FIG. 13 presents another embodiment according to the invention with anarrangement diagram showing an example of watching a display device witha parallel light type filter,

FIG. 14 presents another embodiment according to the invention with anexplanatory diagram of a principal part showing relationships among aplaner light source, a display plane, and a filter,

FIG. 15 presents another embodiment according to the invention with anexplanatory diagram of a principal part showing an example of providinga front filter,

FIG. 16 presents another embodiment according to the invention with anexplanatory diagram of a principal part showing an example of providinga rear filter,

FIG. 17 presents a display device to which the invention is applied,with FIG. 17A being a plan view of an optical system, and FIG. 17B beingan exploded perspective view of a liquid crystal display element,

FIG. 18 presents a display device, to which the invention is applied,with an exploded perspective view of a liquid crystal display element,

FIG. 19 presents a display device to which the invention is applied,with FIG. 19A being an explanatory diagram showing light in a polarizedstate in a half-wave plate, and FIG. 19B being an explanatory diagramshowing light in being incident onto a polarizing filter on the lightsource side, and

FIG. 20 is an explanatory diagram of a principal part presentingproblems in a conventional display device.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In the following, embodiments according to the invention will beexplained with reference to the drawings. First, an explanation will bemade about image separation mechanisms used in the invention withreference to FIG. 17 to FIG. 19. Thereafter, an explanation will be madein detail about a light converging system, a first example as one of theembodiments according to the invention, with reference to FIG. 1 to FIG.9. After a basic explanation is finished here, an example about a lightdiffusing system as a second embodiment according to the invention willbe explained with reference to FIG. 10 to FIG. 12. Furthermore, in FIG.13 to FIG. 16, an example about a parallel light system as a thirdembodiment according to the invention will be explained.

For a display plane used in the invention, a transparent type displaydevice is used which is represented by a slide film or a liquid crystaldisplay element. Moreover, for the image separation mechanism, there area method of using linearly polarized light rays crossing at rightangles, a method of using circularly polarized light rays, a method ofusing light rays with wavelengths thereof different from each other (redand blue etc.), and the like.

The above-described image separation mechanism can be arranged by amethod of providing on both sides of the above-described pixels. This,however, causes a problem in accuracy in positioning them with eachother. Thus the following two methods are often used.

(1) As the above-described image separation mechanism, on a linearlypolarizing plate on the side of an entrance face of the above-describedbacklight, a half-wave plate is provided on every other horizontal line,and on the side of the outgoing light, there is disposed a polarizingplate crossing at right angles to the side of the entrance face.

(2) As the above-described image separation mechanism, on a linearlypolarizing plate on the side of an outgoing face of the above-describedbacklight, a half-wave plate is provided on every other horizontal line,and watching is carried out through two polarizing plates crossing atright angles to each other.

Next to this, an example of arrangement of the above-described imageseparation mechanism and the separation filter is shown in FIG. 17.

In FIG. 17, reference numeral 10 denotes a liquid crystal displayelement contained in a case (not shown) of a liquid crystal displaydevice. On the back side of the liquid crystal display element 10, thereis disposed a Fresnel lens 11 with a specified distance apart therefrom.The Fresnel lens 11 has a lens face with concentric steps on one sidethereof, and makes light, incident from a focal point at the center onthe back side of the Fresnal lens, projected as approximately parallellight.

In front of the liquid crystal display element 10, there is mounted adiffusing plate 12 to project light passing through the liquid crystalelement 10 onto the watcher side via the diffusing plate 12. Moreover,reference numeral 13 denotes a backlight as a light source forilluminating the liquid crystal display element 10 from the rear facethereof. On the front face side (illumination side) of the backlight 13,a polarizing filter unit for the right eye 14 a and a polarizing filterunit for the left eye 14 b are arranged at the right and left,respectively, with the center thereof taken as a boundary. A broken linein FIG. 17A shows the distance of distinct vision.

The respective polarizing filter units for the right and left eyes 14 aand 14 b are arranged as linearly polarizing filters with polarizingdirections thereof made to cross at right angles to each other toprovide, for example, a plane of polarization sloping upward toward theright and a plane of polarization sloping upward toward the left.

The above-described liquid crystal display device 10 is of a transparenttype, which has, as shown in FIG. 17B, a liquid crystal panel 20 and twopolarizing filters 20 and 21 each disposed on each face of the liquidcrystal panel 20. The liquid crystal panel 20 contains, for example, aliquid crystal rotated through 90° inside a pair of alignment films.This makes incident light rotate through 90° to go out when no voltageis applied across a pair of the alignment films. When a voltage isapplied, the incident light is made go out as made incident withoutbeing subjected to any rotation.

Each of the two polarizing filters 21 and 22 is arranged to have on eachhorizontal line of the liquid crystal panel alternately disposedlinearly polarizing filter line units La and Lb, crossing at rightangles to each other, with direction of polarization of each of facinglinearly polarizing filter line units La and Lb on the light source side(rear side) and the watching side (front side), respectively, made tocross at right angles to the other.

Therefore, light from the polarizing filter unit for the right eye 14 aor the polarizing filter unit for the left eye 14 b is allowed to go inonly from the linearly polarizing filter line unit La or Lb having thesame plane of polarization as that of the polarizing filter unit. Thus,the light is to go in every other horizontal line and the light made togo in is transmitted when no voltage is applied and shut when a voltageis applied.

Moreover, an arrangement is provided so that image information for theright eye and image information for the left eye are displayedalternately on the liquid crystal panel 20 of the above-described liquidcrystal display element 10 on each horizontal line in being aligned withlight transmission line of the two polarizing filters 21 and 22.

Therefore, when a watcher watches the liquid crystal display element 10at the distance of distinct vision (near point distance), only light ofan image for the right eye is incident on the right eye 25 a and onlylight of an image for the left eye is incident on the left eye 25 bindependently of each other, which can provide viewing as a stereoscopicimage due to three-dimensional visual perception based on binoculardisparity.

As another example of the above-described liquid crystal element, thereis a liquid crystal element 10 a shown in FIG. 18. In FIG. 18, theliquid crystal element 10 a has a liquid crystal panel 20, and twopolarizing filters 21 a and 22 a each being disposed on each face of theliquid crystal panel 20. The arrangement of the liquid crystal panel 20is the same as that shown in FIG. 17 except differences in arrangementsof two polarizing filters 21 a and 22 b.

Namely, each of the polarizing filters 21 a and 22 a is a linearlypolarizing filter with the plane of polarization being the same over thewhole face. However, the planes of polarization of the two polarizingfilters are provided in directions crossing at right angles to eachother. Furthermore, to the polarizing filter 21 a on the light sourceside, there are attached half-wave plates 26 on every other horizontallines of the liquid crystal panel 20.

The half-wave plate 26 is disposed so that light incident thereon isturned through 90° before going out therefrom as shown in FIG. 19A. InFIG. 19B, polarized light sloping upward toward the left can not passthrough a line of the polarizing filter 21 a without the half-wave plate26. While, with the half-wave plate 26, the polarized light is turnedthrough 90° to be polarized light sloping upward toward the right, whichcan pass through the line of the polarizing filter 21 a. Conversely,polarized light sloping upward toward the right can pass through a lineof the polarizing filter 21 a without the half-wave plate 26. While,with the half-wave plate 26, the polarized light is turned through 90°to be polarized light sloping upward toward the left, which can not passthrough the line of the polarizing filter 21 a.

In addition, the direction of polarization of all of the lightimmediately after being incident on the polarizing filter 21 a on thelight source side becomes upward toward the right. Therefore, all ofdirections of polarization of the polarizing filter 22 a on the watchingside can be a direction upward toward the left to result in costreduction.

Moreover, instead of the above-described linearly polarized light,circularly polarized light can be used. Further, instead of theabove-described Fresnel lens 11, a concave mirror can be used.

FIG. 1 to FIG. 9 relate to an example of a system of converging light asone of a first embodiment according to the invention. In the figures, apixel member 31 of a liquid crystal element 30 has an arrangement inwhich a first image region (a pixel region displaying a first image) anda second image region (a pixel region displaying a second image) arealternately formed in the vertical direction, and an image separationfilter 32 has an arrangement in which a first image separation mechanismand a second image separation mechanism are alternately formed in thevertical direction. The above-described pixel member 31 and the imageseparation filter 32 are mounted via transparent glasses 33 and 34(specified regions) each having a specified thickness.

FIG. 1 is a view in which there are drawn from the side optical paths oneach of which a light beam emitted from a light source 35 passes througha specified image region on a display plane toward a watcher. This is anoptical system in which the light beam emitted from the light source 35disposed in proximity to a converging point of first optical means isincident on the first optical means 36 (for example, a convex lens etc.)to illuminate the display plane and passes through the image separationfilter 32 on the display plane before being converged toward a positionof a head of the watcher.

In the invention, as shown in FIG. 2 and FIG. 3, in a region on a lightbeam passed through the first image region s₁, the first imageseparation mechanism e₁ is disposed without the second image separationmechanism e₂ being disposed. Furthermore, in a region on a light beampassed through the second image region S₂, the second image separationmechanism e₂ is disposed without the first image separation mechanism e₁being disposed. In order to provide such a disposition, an optical pathof a light beam corresponding to an image region of each pixel is tracedso as to provide each of the image separation mechanism e₁ and e₂ foreach region connecting cross points of the optical paths and a filterattaching plane.

A state of the pixel and the image separation filter at this time isshown in an enlarged view in FIG. 2 or in FIG. 3 with FIG. 2 showing anexample of disposing the image separation filter on the side of adisplay plane watcher and FIG. 3 showing that on the back side.

This makes the light beam passing through the first image region s₁ ofthe pixel member 31 surely pass through the first image separationmechanism e₁ of the image separation filter 32, and the light beampassing through the second image region s₂ of the pixel member 31 surelypass through the second image separation mechanism e₂ of the imageseparation filter 32, by which separation is surely carried out withoutcausing the light beam to enter the other image separation mechanism togenerate no crosstalk between images.

Next, with reference to FIG. 4 to FIG. 8, with the converging rearfilter disposing type shown in FIG. 3 taken as an example, a conditionof arranging the image separation filter will be examined specificallyin detail with the explanation thereof.

A condition is provided in which an interval between each of the imageregions of the pixel member 31 on the display plane is taken as anuniform interval of P2 and an watcher is at a light converging point ofthe optical means 36, with a distance from the display plane taken as D.Let the above-described glasses 33 and 34 have thicknesses W1 and W2from the watcher side, respectively, with refractive index of each ofthem equally taken as n. A width of the image separation filter 32 (adisposing interval between the image separation mechanisms) at this timewill be obtained which is required in watching a K-th pixel from thecenter of the display plane.

Moreover, in the pixel member 31 in the embodiment, the disposinginterval P2 between the second image regions is the width of the firstimage region, and a disposing interval between the first image regionsis the width of the second image region.

Furthermore, in the image separation filter 32 in the embodiment, thedisposing interval P1 or P3 between the second image separationmechanisms is the width of the first image separation mechanism, and adisposing interval between the first image separation mechanisms is thewidth of the second image separation mechanism.

Let angles of elevation to vertical end lines of the K-th and (K+1)-thpixels from the watching point be θk+1 and θk, respectively, and letangles of light beams in correspondence therewith that pass through theglasses 33 and 34 be αk+1 and αk as shown in the figure.

Furthermore, on the basis of the above-described angles of elevationθk+1 and θk, angles αk+1 and αk, thicknesses W1 and W2 and refractiveindex n of the glasses 33 and 34, distance D from the watching point tothe display device, and interval (P2) between the image regions of thepixel 31, calculations are carried out which are for obtaining thedisposing intervals (P1 or P3) between each of the image separationmechanisms of the image separation filter 32. This allows to obtain P1(the disposing interval between the second image separation mechanisms,that is, the vertical width of the first image separation mechanism)when providing the filter in front of the display plane watcher as shownin the figure, and P3 (the disposing interval between the second imageseparation mechanisms, that is, the vertical width of the first imageseparation mechanism) when providing the filter on the back side.

The above calculations are as follows.

In FIG. 4, the angles of elevations are under conditions of0°≦θ_(k)<90°, and 0°≦θ_(k+1)<90°. From n sin α_(k)=sin θ_(k) (Snell'slaw), there is obtained as,

$\begin{matrix}\begin{matrix}{{\tan\;\alpha_{k}} = {\left( {\sin\;{\alpha_{k}/\cos}\;\alpha_{k}} \right) = {\left( {\sin\;{\theta_{k}/n}} \right)/\left\{ {1 - \left( {\sin\;{\theta_{k}/n}} \right)^{2}} \right\}^{1/2}}}} \\{= {\left( {\sin\;{\theta_{k}/n}} \right)\left\{ {n^{2}/\left( {n^{2} - {\sin^{2}\;\theta_{k}}} \right)} \right\}^{1/2}}} \\{= {\sin\;{\theta_{k}/{\left( {n^{2} - {\sin^{2}\;\theta_{k}}} \right)^{1/2}.}}}}\end{matrix} & (1)\end{matrix}$

Furthermore, from FIG. 4, there is given as,kP2=D tan θ_(k) +w1 tan α_(k)  (2).Then, substitute the expression (1) into the expression (2), we havekP2=D sin θ_(k)/(1−sin²θ_(k))^(1/2) +w1 sin θ_(k)/(n²−sin²θ_(k))^(1/2)  (3).

Here, if we let sin θ_(k)≡t, we havef(t)≡kP2(1−t ²)^(1/2)(n ² −t ²)^(1/2) −Dt(n ² −t ²) ^(1/2) −W1t(1−t²)^(1/2)  (4).

Since 0°≦θ_(k)<90°, we have 0≦t<1. Then, letting k be a constant, thereis obtained t that makes f(t)=0, which is renewed as a constant t.

Letting t=sin θ_(k), and similarly T≡sin θ_(k)+1 for k+1, P3 and P1 areobtained as,P3=P2+w2{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)}  (5)P1=P2−w1{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)}  (6),where,{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)}=(tan α_(k+1)−tan α_(k))  (7)

The above expression (2) expresses a height (distance) from the centerof the display plane to the K-th pixel 31. Dispositional relationbetween the pixel 31 (for example, the first image region) and the imageseparation filter 32 (for example, the first image separation mechanism)is as shown in FIG. 6 with relational expressions about the providingdistance between them given as follows:W1*tan α_(k) =W1*t/(n ² −t ²)^(1/2)  (8)W2*tan α_(k) =W2*t/(n ² −t ²)^(1/2)  (9)where t is the t used in the above-described expression (5) andexpression (6), for which sin θ_(k) for f(t)=0 in the above-describedexpression (4) is taken as t. Moreover, FIG. 6B shows inside of theround mark with a broken line in FIG. 6A.

In the following, FIG. 4 is examined with specific values with referenceto FIG. 5 to FIG. 9. FIG. 5 shows how to obtain the constants t and T inthe above-described operation expressions, by which values of f(t) and tin FIG. 4 are obtained under the condition shown in the figure. From thegraph in FIG. 5, for K=128, there are obtained approximately ast=0.0596655 and T=0.0601300. By the above-explained operationexpressions, P1 of the filter on the front side is obtained asP1=0.280179758, a little smaller than 0.2805 of the pixel width (P2).Further, P3 on the back side is obtained as P3=0.280820242, a littlelarger than the pixel width (P2).

With a display device arranged with thus obtained widths P2, P1, and P3,relationship between the pixel and filters at k=128 is shown in FIG. 7.As is apparent from the FIG. 7, a light beam from a light source Jpassing through the first pixel separation mechanism e₁ (P3 and P1)toward a watcher I can pass through the first image region s₁ (P2) only.Thus, by making differences between P2 and P1, and P2 and P3 as beingabout ±0.3 microns, generation of crosstalk of the image could be surelyprevented.

FIG. 8 shows values of P3, obtained by the methods shown in FIG. 4 andFIG. 5, plotted about K. As is apparent from FIG. 8A, the value of P3 isabout 0.2808 and approximately constant. It is understood that, as isapparent from the graph of FIG. 8B, an enlarged view of FIG. 8A, thewidth of P3 tends to narrow with an increase in the distance from thecenter of the display plane (that is, k).

However, the pixel at k=1000 is in this case a distance from the centerof 0.2805*1000=280.5 (mm), which provides, with D=600 (mm) taken intoconsideration, an angle of elevation of θ=25.0560°, a very large angleof looking up. Supposing that the display has an aspect ratio of 4:3,the above becomes also apparent from the fact that this corresponds towatching a 36.8 inch display at a short distance of 60 cm therefrom.With respect to an angle of view and k larger than the above, the deviceis not actual. Therefore, for a fixed pixel width P2, a width P1 or P3of the image separation filter can be actually substituted by an alwaysfixed one.

FIG. 9 shows values of P3 to the distance D in the depth direction. Itis understood that the change in P3 is not so large for D=500 to 700(mm), and that the width (P3) of the rear filter tends to become narrowwith an increase in the distance in the depth direction.

The above examination on the optical paths passing the pixels on thedisplay plane, carried out with a converging type taken as an examplewith reference to FIG. 1 to FIG. 9, showed that an image separationfilter can be brought into realization without any crosstalk by theother image.

Next, with reference to FIG. 10 to FIG. 12, characteristics of the imageseparation filter according to the invention will be explained about thecase with a diffusing type optical system. FIG. 10 shows a schematicarrangement with a case used in a projection system taken as an example.It is an example in which light emitted from a light source 35 isdiverged through a second optical means 46 and illuminates the wholedisplay plane before being diffused to be projected on a screen 40 as animage being served to enjoyment. Also in the example, like in theprevious example, each of FIG. 11 and FIG. 12 shows a state of a lightbeam passing a pixel.

As is apparent from the figures, it is understood that an arrangementmust be provided so that, in FIG. 11 in which the image separationfilter 32 is provided on the side opposite to a light source J about adisplay plane (on the side of a screen SC), a width of the filterbecomes wider than a width of the pixel, and conversely, in FIG. 12 inwhich the image separation filter 32 is provided on the inner side ofthe display plane (on the side of the light source J), the width of thefilter becomes narrower than the width of the pixel. The widths of thefilters and the widths of the pixels are obtained by the same method asthat in the example of the converging type explained with reference toFIG. 1 to FIG. 9.

However, although the operation expressions for obtaining disposingintervals (P1 and P3) of the image separation mechanisms of the imageseparation filter 32 in the case with the diffusion type optical systemare theoretically the same as those in the above, there is a littledifference in each of the parameters. Namely, let angles of elevation tovertical end lines of the K-th and (K+1)-th pixels from the light source35 be θk+1 and θk, respectively, and let angles of light beams incorrespondence therewith that pass through the glasses 33 and 34 be αk+1and αk.

Furthermore, on the basis of the above-described angles of elevationθk+1 and θk, angles αk+1 and αk, thicknesses W1 and W2 and refractiveindex n of the glasses 33 and 34, distance D from the watching point tothe display device, and interval (P2) between the image regions of thepixel 31, calculations are carried out which are for obtaining thedisposing intervals (P1 or P3) between each of the image separationmechanisms.

When the image separation filter 32 is provided on the screen sideopposite to the light source as FIG. 11, the width of the filter isarranged to be wider than the pixel width. Therefore, in conformity tothe above-described expression (5), calculation of an operationexpression ofP3=P2+w1{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)}  (10)is carried out to obtain the filter width (P3).

Moreover, when the image separation filter 32 is provided on the lightsource side as FIG. 12, the width of the filter is arranged to benarrower than the pixel width. Therefore, in conformity to theabove-described expression (6), calculation of an operation expressionofP1=P2−w2{T/(n ² −t ²)^(1/2) −t/(n ² −t ²)^(1/2)}  (11)is carried out to obtain the filter width (P1).

Here, a projection system is taken as the example. The system, however,can be any one in which the light beam passing through the display planeis in the direction of diffusion therein, so that the invention can beapplied also to an optical system such that a small display plane islooked in.

In FIG. 13 to FIG. 16, an example of an image separation filteraccording to the invention as the case with a parallel type opticalsystem. FIG. 13 shows an example in which a light source 35 is disposedin proximity to a light converging point of third optical means 56 toprovide parallel light passing through a display plane filter unit (aliquid crystal element 30) before being made converged in proximity toahead of a watcher by fourth optical means. In this case, in order toincrease utilization efficiency of light, the fourth optical means 66 isdisposed. However, there can be no problem even though no fourth opticalmeans 66 is provided.

FIG. 14 shows an example in which parallel light is emitted from aplane-like light source 45 in the vertical direction to a display planefilter unit (a liquid crystal display 30) and light passed through thedisplay plane filter unit (parallel light) is watched. An arrangement ofthe image separation filter 32 in this case is, as shown in FIGS. 15 and16, only requires the pixel 31 and the image separation filter 32 tohave uniform widths and to be disposed at positions to which they arelaterally shifted from the arrangement shown in FIG. 1 to FIG. 3 andFIG. 10 to FIG. 12. Moreover, when the light beam is provided asinclined parallel light, each of them is provided to have a uniformwidth, but required to be shifted by a shift from the pixel.

In the explanation of the above-described embodiments, the width of thefirst image regions of the pixel member 31 (the disposing interval ofthe second image regions) was taken as P2. However, it is not necessaryto be limited to this, but calculation can be carried out with the widthof the second image regions (the disposing interval of the first imageregions) taken as P2.

Similarly, although the width of the first image separation mechanismsof the image separation filter 32 (the disposing interval between thesecond image separation mechanisms) was taken as P1 or P3, it is notnecessary to be limited to this, but the width of the second imageseparation mechanism (the disposing interval between the first imageseparation mechanisms) can be taken as P1 or P3 to carry outcalculation.

Furthermore, the embodiments in the method of designing the displaydevice according to the invention is, by carrying out the methodexplained with reference to the above-explained FIG. 4 to FIG. 9 andpresented as the above-described operation expressions, to dispose thefirst image separation mechanism in a region on a light beam passedthrough the first image region without the second image separationmechanism being disposed, and to dispose the second image separationmechanism in a region on a light beam passed through the second imageregion without the first image separation mechanism being disposed.

In addition, the arrangement of the display device according to theinvention is provided with each of the elements explained with referenceto FIG. 17 to FIG. 19. Namely, the first and second image separationmechanisms are linearly polarized light rays crossing at right angles toeach other or circularly polarized light rays with directions thereofdifferent from each other, or wavelengths different from each other suchas red and blue etc.

Furthermore, the above-described first and second image separationmechanisms are arranged with linearly polarized light rays crossing atright angles to each other, half-wave plates, and the like.

Moreover, the above-described first and second image separationmechanisms are to be arranged with linearly polarized light rayscrossing at right angles to each other and half-wave plates, in which,on the linearly polarizing plate on the side of an entrance face oflight of the above-described display plane, each half-wave plate isprovided on every other horizontal line, and on the side of the outgoinglight, there is disposed the polarizing plate crossing at right anglesto the side of the entrance face.

Further, the above-described first and second image separationmechanisms are provided with the half-wave plates each on every otherhorizontal line on the linearly polarizing plate on the side of anoutgoing face of light, and watching is carried out through a polarizingplate with direction of polarization thereof crossing at right angles tothat of the polarizing plate.

As described above, the display device according to the presentinvention can carryout the separation display without providing anyimage separation mechanism within the pixel without causing anycrosstalk between the first image region and the second image region.

Moreover, image resolution is improved to allow to make it possible toenjoy a stereoscopic image without any crosstalk between the right andleft images. Further, image resolution is improved to make it possibleto enjoy views with a plurality of images without any crosstalk betweenthe first and second images.

Furthermore, with the method of designing the display device accordingto the invention, a display device can be simply and easily designedwhich can carryout the separated display without providing any imageseparation mechanism within the pixel without causing any crosstalkbetween the first image region and the second image region.

In addition, quick and free design of the image separation filter of thedisplay device becomes possible. Besides, image resolution is improvedto make it possible to enjoy a stereoscopic image without any crosstalkbetween the right and left images. Further, image resolution is improvedto make it possible to enjoy views with a plurality of images withoutany crosstalk between the first and second images.

INDUSTRIAL APPLICABILITY

The invention, being not limited to the above examples of embodiments,can be applied to display devices with other arrangements for displayingstereoscopic images with binocular disparities or displaying multi-viewsfrom one displayed image.

1. A method of designing a display device having a transparent displayelement transmitting light projected from a light source to an watchingpoint, and comprising a pixel member formed with a first image regionand a second image region, and an image separation filter separated fromthe pixel member by a specified region and formed with a first imageseparation mechanism and a second image separation mechanism, thedesigning method characterized in that a disposing interval of each ofsaid image separation mechanisms is determined by carrying out acalculation for obtaining the disposing interval on the basis of anangle formed by a straight line connecting said watching point and anend point of the image region of said pixels, with respect to aperpendicular line from the watching point to the display device, athickness and a refractive index of said specified region, a length ofsaid perpendicular line, and an interval of the image regions of saidpixel member, and the first and second image separation mechanisms ofsaid image separation filter are arranged to cause light to be polarizedin directions of polarization different from each other.